Summary

This is a ball mount for a small mirror which allows rotation about any axis. The mirror rim is 52.5 mm diameter by 4.88 mm thick.

Instructions

Glue (with acetone) the ball_141114b.stl to mirror_mount_141113b.stl. Glue clip_141114g.stl to mount_141115.stl. snap the ball into clip_141114g.stl. Use double stick foam tape to attach to top of monitor.

Some of the design concepts:
The ball diameter is 20 mm.
The 3 arms have 20 mm ball diameter indents. However the arms have been moved inward 0.5 mm to provide a slight preload on the ball to keep in place.

The preload will be sensitive to the arm length and inward movement of the three arms in clip_141114g.stl. A higher preload will hold the mirror in place more tightly. Shorter arms increase the ball preload because they will be stiffer (proportional to L^3). Moving the arm radially inward more also increases the preload. The limit to these two effects is that the arms will break when inserting the ball.

If you use the design concept for other applications, please share with the community.